It says most of the popular tire sizes are smaller than what is programed to the speedo. We are acturally going slowere than we think. 225/40/18 is off by 0.9% and 225/45/17 is off by 1.4%. Well I guess this is not too bad. But 215/45/17 is off by 2.8% and my stocker for now 205/60/15 is off by 2.5%. Now this can make a diffference. The perfect fit would be 235/45/17.

I am in the market for new wheels now and I am not sure if I want to pay a bit more to get the 235/45/17 tires.

audi_a4_kid

03-09-2005, 12:35 PM

with 16's top speed =130
with 17's top speed =127

pigliiit

03-09-2005, 12:45 PM

here's a link to the one i use.

http://www.miata.net/garage/tirecalc.html

mmart6545

03-09-2005, 12:56 PM

Originally posted by audi_a4_kid
with 16's top speed =130
with 17's top speed =127

???

quickglx

03-09-2005, 05:43 PM

There are several sizes that come on these cars from the factory, so what perfect tire size are you comparing to? Even different manufacturers tires of the same size are slightly different sizes. Difference between some manufacturers 235s and some 225s are like the difference between new and bald tires. Also the difference price wise isn't too bad either. I went w/ the 235/45/17s regardless.... I wanted a little more cushion in the sidewalls, praying for more grip too.